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111 lines
3.0 KiB
GLSL
111 lines
3.0 KiB
GLSL
// Author: @patriciogv - 2015
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// Tittle: Turbulence
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#ifdef GL_ES
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precision mediump float;
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#endif
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uniform vec2 u_resolution;
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uniform vec2 u_mouse;
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uniform float u_time;
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// Some useful functions
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vec3 mod289(vec3 x) { return x - floor(x * (1.0 / 289.0)) * 289.0; }
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vec2 mod289(vec2 x) { return x - floor(x * (1.0 / 289.0)) * 289.0; }
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vec3 permute(vec3 x) { return mod289(((x*34.0)+1.0)*x); }
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//
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// Description : GLSL 2D simplex noise function
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// Author : Ian McEwan, Ashima Arts
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// Maintainer : ijm
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// Lastmod : 20110822 (ijm)
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// License :
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// Copyright (C) 2011 Ashima Arts. All rights reserved.
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// Distributed under the MIT License. See LICENSE file.
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// https://github.com/ashima/webgl-noise
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//
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float snoise(vec2 v) {
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// Precompute values for skewed triangular grid
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const vec4 C = vec4(0.211324865405187,
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// (3.0-sqrt(3.0))/6.0
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0.366025403784439,
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// 0.5*(sqrt(3.0)-1.0)
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-0.577350269189626,
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// -1.0 + 2.0 * C.x
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0.024390243902439);
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// 1.0 / 41.0
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// First corner (x0)
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vec2 i = floor(v + dot(v, C.yy));
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vec2 x0 = v - i + dot(i, C.xx);
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// Other two corners (x1, x2)
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vec2 i1 = vec2(0.0);
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i1 = (x0.x > x0.y)? vec2(1.0, 0.0):vec2(0.0, 1.0);
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vec2 x1 = x0.xy + C.xx - i1;
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vec2 x2 = x0.xy + C.zz;
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// Do some permutations to avoid
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// truncation effects in permutation
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i = mod289(i);
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vec3 p = permute(
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permute( i.y + vec3(0.0, i1.y, 1.0))
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+ i.x + vec3(0.0, i1.x, 1.0 ));
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vec3 m = max(0.5 - vec3(
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dot(x0,x0),
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dot(x1,x1),
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dot(x2,x2)
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), 0.0);
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m = m*m ;
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m = m*m ;
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// Gradients:
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// 41 pts uniformly over a line, mapped onto a diamond
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// The ring size 17*17 = 289 is close to a multiple
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// of 41 (41*7 = 287)
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vec3 x = 2.0 * fract(p * C.www) - 1.0;
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vec3 h = abs(x) - 0.5;
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vec3 ox = floor(x + 0.5);
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vec3 a0 = x - ox;
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// Normalise gradients implicitly by scaling m
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// Approximation of: m *= inversesqrt(a0*a0 + h*h);
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m *= 1.79284291400159 - 0.85373472095314 * (a0*a0+h*h);
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// Compute final noise value at P
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vec3 g = vec3(0.0);
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g.x = a0.x * x0.x + h.x * x0.y;
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g.yz = a0.yz * vec2(x1.x,x2.x) + h.yz * vec2(x1.y,x2.y);
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return 130.0 * dot(m, g);
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}
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#define OCTAVES 3
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float turbulence (in vec2 st) {
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// Initial values
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float value = 0.0;
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float amplitude = .5;
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float frequency = 0.;
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//
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// Loop of octaves
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for (int i = 0; i < OCTAVES; i++) {
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value += amplitude * abs(snoise(st));
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st *= 2.;
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amplitude *= .5;
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}
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return value;
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}
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void main() {
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vec2 st = gl_FragCoord.xy/u_resolution.xy;
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st.x *= u_resolution.x/u_resolution.y;
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vec3 color = vec3(0.0);
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color += turbulence(st*3.0);
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gl_FragColor = vec4(color,1.0);
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}
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